This invention relates to a process for producing a benzophenone-azine which is an intermediate used for producing hydrazine from benzophenones.
Many processes for producing benzophenone-azines by oxidizing benzophenone-imines are known in the art. A process for producing a benzophenone-azine by oxidizing benzophenone-imines in the presence of a copper halide, particularly cuprous chloride, is known from U.S. Pat. No. 2,870,206. A process for producing a benzophenone-azine by contacting a benzophenone in pyridines with ammonia and molecular oxygen in the presence of cuprous chloride and ammonium chloride or zinc chloride is known from Japanese Patent Publication (laid open) No. 7942/1977. A process for producing a benzophenone-azine by oxidizing a benzophenone-imine in the presence of excess amount of pyridine by using copper (II) halide methoxide is known from Japanese Patent Publication (laid open) No. 147047/1978. Japanese Patent Publication (laid open) No. 71045/1978 discloses that copper acetates, copper thiocyanade, copper cyanide and the like are useful for preparing benzophenone-azines from benzophenone-imines. Japanese Patent Publication (laid open) No. 131987/1977 (U.S. Pat. No. 4,079,080) discloses that a high molecular catalyst obtained by incorporating cuprous halide in a resin, the functional group of which is pyridines, is useful for oxidizing benzophenone-imines.
However, these processes need expensive copper salt as a catalyst. When copper salts are used as liquid phase homogeneous catalyst, it is necessary to control the valency of the copper, to keep the ratio of copper ion to negative ion constant, or to introduce a ligand, such as expensive pyridine, into the catalyst for preventing the decrease in the reaction activity. In addition, since the prior catalyst is dissolved in the reaction solution, the prior processes need complicated operations to recover copper salt as a catalyst from the solution. For example, operations such as separation of the copper salt from the solution and regeneration of the copper catalyst, etc. are necessary. So, the process increases the investment of equipment and incurs a loss of energy for operation. Further, expensive anticorrosive material should be used for making equipment in order to prevent corrosion of the equipment by halogen constituting the catalyst. Accordingly, the processes are unsuitable from an industrial point of view.
When high molecular catalyst coordinated copper ion by a ligand, functional group of which is pyridines is used, copper ion is released from the catalyst during the reaction and is not completely on the catalyst even at the end of the reaction. The process is not proper in spite of using a particular resin.